The present invention relates to the preparation of enantiomerically enriched hydroxychromanones by the AlCl3-catalyzed intramolecular Friedel-Crafts acylation of the corresponding 3-phenoxy-2-alkylcarbonyloxy-propionic acid followed by cleavage of the carboxylate in the presence of an alkali metal peroxide or hydroperoxide. The present invention further relates to the preparation of enantiomerically enriched cis-aminochromanols by the diastereomeric reduction of oximes derived from the hydroxychromanones. The cis-aminochromanols are useful as intermediates in the preparation of HIV protease inhibitors.
References are made throughout this application to various published documents in order to more fully describe the state of the art to which this invention pertains. The disclosures of these references are hereby incorporated by reference in their entireties.
cis-Aminochromanols are useful as intermediates in the preparation of HIV protease inhibitor compounds, which can be used to treat HIV infection, AIDS and ARC. EP 434,365 discloses, inter alia, a series of N-substituted 2(R)-((morpholinyl-ethoxy)phenylmethyl)-5(S)-((dimethylethoxycarbonyl)amino)-4(S)-hydroxy-6-phenyl-hexanamide derivatives which are useful as HIV protease inhibitors, including inhibitors prepared using cis-aminochromanol. In particular, reference is made to Example 21 of EP ""365. U.S. Pat. No. 5,413,999 discloses certain N-substituted 2(R)-phenylmethyl-4(S)-hydroxy-pentaneamide derivatives which are useful as HIV protease inhibitors, including inhibitors which can be prepared from cis-aminochromanol. Reference is made, for example, to Table 1 of U.S. ""999, the third entry in cols. 33-34.
The HIV protease inhibitor compounds typically have asymmetric centers, and the active form is often a particular enantiomer or diastereomer of the compound. In order to avoid a potentially complex and time-consuming resolution of the desired enantiomer or diastereomer from a mixture of optical isomers, it is desirable to prepare a relatively pure form of the active isomer directly using the appropriate optically active intermediates. Accordingly, it is also desirable to have an efficient, practical route for preparing optically enriched forms of cis-aminochromanols and also for preparing optically enriched forms of any intermediates and precursors thereof having chiral centers.
The present invention is directed to an efficient route for preparing optically enriched hydroxychromanones, the subsequent use of the hydroxychromanones for preparing optically enriched hydroxychromanone oximes, and the use of the oximes for preparing optically enriched cis-aminochromanols.
The following references are of interest as background:
Sethna, xe2x80x9cCycliacylationxe2x80x9d, Chapter XXXV in Friedel-Crafts and Related Reactions, Vol. III, part 2, Interscience, 1964, pages 911-1002, describes the formation of cyclic compounds via intramolecular Friedel-Crafts acylations, such as the formation of cyclic ketones from arylaliphatic acids.
Kajiro et al., Bull. Chem. Soc. Jap. 1999, 72: 1093-1100, discloses the preparation of (R)-2-hydroxy-1-indanone by the intramolecular Friedel-Crafts acylation of (R)-2-acetoxy-3-phenylpropanoic acid. Kajiro et al. further discloses the preparation of the corresponding hydroxyindanone oxime from (R)-2-hydroxy-1-indanone, and then hydrogenating the oxime in the presence of HBr and Pd black to obtain (1S,2R)-1-amino-2-indanol.
Bognar et al., Tetrahedron 1963, 19: 391-394, discloses the preparation of 4-amino-3-hydroxyflavan by the hydrogenation of the corresponding oxime in the presence of PtO2 at atmospheric pressure in warm aqueous (80%) acetic acid. Bognar et al., Tet. Letters 1959, No. 19: 4-8, has a similar disclosure.
Julian et al., J. Het. Chem. 1975, 12: 1179-1182, discloses the preparation of cis-4-aminochroman-3-ol by reaction of 2-oxo-1,3a,4,9b-tetrahydro-2H[1]benzo-pyrano[4,3-d]oxazole with methanolic potassium hydroxide. EP 434,365 discloses substantially the same preparation in Example 21, Steps A and B.
Ghosh et al., Tet. Letters 1991, 32: 711-714, discloses the preparation of 4-aminothiochroman-3-ol by the reduction of the corresponding xcex1-hydroxy benzyloxime with borane in tetrahydrofuran. It is further disclosed that borane reduction of an equilibrium mixture (3:2) of the anti and syn oximes afforded a 90/10 mixture of the cis/trans 4-aminothiochroman-3-ols.
U.S. Pat. No. 6,057,479 (Mitamura et al.) discloses the preparation of cis-1-amino-2-indanol by the catalytic hydrogenation of 2-hydroxy-1-indanone oxime in methanol. Example 21 of U.S. ""479 discloses the hydrogenation in the presence of Pd black and HCl to give an aminoindanol product having a cis/trans selectivity of 95.5:4.5. Examples 22-23 report similar results for analogous hydrogenations using Pd/C and Pd/alumina. Example 24 discloses an analogous hydrogenation using Pd black and aqueous HBr to provide 1-amino-2-indanol product with a cis/trans ratio of 95.6:4.4. Results substantially the same as in Example 24 are also reported in Kajiro et al., SYNLETT 1998, p. 51.
The present invention is directed to an efficient process for preparing enantiomerically enriched 3-hydroxychroman-4-ones via the intramolecular Friedel-Crafts acylation of the corresponding 3-phenoxy-2-alkylcarbonyloxy-propionic acid followed by cleavage of the carboxylate group in the presence of an alkali metal peroxide or hydroperoxide. More particularly, the present invention is a process for preparing a hydroxychromanone of Formula (I): 
which comprises:
(C) adding an acid halide of Formula (II-C): 
xe2x80x83to a solution of AlCl3in a first organic solvent at a temperature of less than about 0xc2x0 C. to form an alkylcarbonyloxy chromanone of Formula (III): 
and
(D) reacting Compound III with an alkali metal peroxide or hydroperoxide in a second organic solvent at a temperature of less than about 0xc2x0 C. to form Compound I;
xe2x80x83wherein:
stereocenter xcex1 is in the R configuration or the S configuration;
each R1 is independently halo, C1-C6 alkyl, halogenated C1-C6 alkyl, C1-C6 alkoxy, halogenated C1-C6 alkoxy, xe2x80x94CO2Ra, xe2x80x94CORa, xe2x80x94NRaRb, xe2x80x94NRaxe2x80x94CORb, xe2x80x94NRaxe2x80x94CO2Rb, xe2x80x94COxe2x80x94NRaRb, xe2x80x94OCOxe2x80x94NRaRb, xe2x80x94NRaCOxe2x80x94NRaRb, xe2x80x94S(O)pxe2x80x94Ra, wherein p is an integer from 0 to 2, xe2x80x94S(O)2xe2x80x94NRaRb, xe2x80x94NRaS(O)2xe2x80x94Rb, or xe2x80x94NRaS(O)2xe2x80x94NRaRb;
R2 is C1-C6 alkyl;
X is halo;
each Ra and Rb is independently hydrogen, C1-C4 alkyl, or (CH2)0-3CF3; and
m is an integer from 0 to 4.
The process of the invention can be conducted with the occurrence of little or no racemization. It has unexpectedly been found that the order of addition of the reactants and the reaction temperature in Step C of the process of the invention are key factors for minimizing racemization. More particularly, processes essentially the same as the process of the invention except that (i) AlCl3 is added to a solution of the acid halide (versus addition of acid halide to an AlCl3 solution) and/or (ii) the acylation is conducted at a temperature above 0xc2x0 C. (versus temperatures below 0xc2x0 C.) will typically afford a hydroxychromanone product having a comparatively much higher degree of racemization and a greater loss of enantiomeric excess. It has also unexpectedly been found that the use of an alkali metal peroxide or hydroperoxide (e.g., LiOOH) and low temperatures in the Step D carboxylate cleavage (e.g., deacetylation) is important for minimizing product racemization; i.e., processes which are the same as the process of the invention except for the use of reagents other than akali metal (hydro)peroxides for the cleavage of the carboxylate (e.g., strong acids such as sulfuric acid and hydrochloric acid) and/or a higher reaction temperature will typically result in a hydroxychromanone product having much greater racemization.
The present invention also includes a process for preparing an aminochromanol of Formula (VII): 
in which the stereocenters xcex1 and xcex2 are either both in the R configuration or both in the S configuration, wherein the process comprises Steps C and D for preparing hydroxychromanone I as defined and described above, and further comprises
(E) treating hydroxychromanone I with a hydroxylamine of Formula (V):
H2Nxe2x80x94OR3xe2x80x83xe2x80x83(V),
xe2x80x83or an acid salt thereof, to form an oxime of Formula (VI): 
xe2x80x83wherein R3 is
(1) hydrogen;
(2) C1-C6 alkyl;
(3) C1-C6 alkyl substituted with one or more substituents, each of which is independently halo, cyano, C1-C4 alkoxy, C1-C4 haloalkoxy, C3-C8 cycloalkyl, or phenyl;
(4) C3-C8 cycloalkyl;
(5) C3-C8 cycloalkyl substituted with one or more substituents, each of which is independently halo, cyano, C1-C4 alkyl, C1-C4 haloalkyl, C1-C4 alkoxy, C1-C4 haloalkoxy, or phenyl;
(6) phenyl; or
(7) phenyl substituted with one or more substituents, each of which is independently C1-C4 alkyl, C1-C4 haloalkyl, C1-C4 alkoxy, C1-C4 haloalkoxy, cyano, or halo; and
(F) hydrogenating in the presence of a palladium catalyst a mixture comprising Compound VI, a third organic solvent, and HBr to form an aminochromanol of Formula (VII).
It has been found that the mixture of E and Z oximes resulting from Step E can be hydrogenated in Step F to provide a relatively high yield of aminochromanol with high cis over trans selectivity. Hydrogenation processes similar to Step F, except for the substitution of HBr with another acid reagent and/or the substitution of Pd with another hydrogenation catalyst, have typically been found to have lower aminochromanol yields and/or lower cis/trans selectivities. Overall, the process constitutes an efficient method for synthesizing cis-aminochromanol in an enantiomerically enriched form using inexpensive and readily available starting materials.
Other embodiments, aspects and features of the present invention are either further described in or will be apparent from the ensuing description, examples and appended claims.
The present invention includes a process for preparing enantiomerically enriched 3-hydroxychroman-4-ones via the intramolecular Friedel-Crafts acylation of the corresponding 3-phenoxy-2-alkylcarbonyloxy-propionic acid (e.g., 3-phenoxy-2-acetoxy-propionic acid) followed by cleavage of the carboxylate group (e.g., deacetylation) in the presence of an alkali metal peroxide or hydroperoxide (e.g., LiOOH). This process is set forth in the Summary of the Invention as Steps C and D. In one embodiment, the present invention is a process for preparing a hydroxychromanone of Formula (I*): 
which comprises:
(C) adding an acid halide of Formula (II-C*): 
xe2x80x83to a solution of AlCl3in a first organic solvent at a temperature of less than about 0xc2x0 C. to form an alkylcarbonyloxy chromanone of Formula (III*): 
and
(D) reacting Compound III* with an alkali metal peroxide or hydroperoxide in a second organic solvent at a temperature of less than about 0xc2x0 C. to form Compound I*;
xe2x80x83wherein R1, R2, X and m are as defined above.
In this process, each group R1 in the definition of Compounds I, II-C, and III is independently halo, C1-C6 alkyl, halogenated C1-C6 alkyl, C1-C6 alkoxy, halogenated C1-C6 alkoxy, xe2x80x94CO2Ra, xe2x80x94CORa, xe2x80x94NRaRb, xe2x80x94NRa13 CORb, xe2x80x94NRaxe2x80x94CO2Rb, xe2x80x94COxe2x80x94NRaRb, xe2x80x94OCOxe2x80x94NRaRb, xe2x80x94NRaCOxe2x80x94NRaRb, xe2x80x94S(O)pxe2x80x94Ra, wherein p is an integer from 0 to 2, xe2x80x94S(O)2xe2x80x94NRaRb, xe2x80x94NRaS(O)2xe2x80x94Rb, or xe2x80x94NRaS(O)2xe2x80x94NRaRb. In one embodiment, each R1 is independently halo, C1-C6 alkyl, halogenated C1-C6 alkyl, C1-C6 alkoxy, or halogenated C1-C6 alkoxy. In another embodiment, each R1 is independently halo, C1-C4 alkyl, halogenated C1-C4 alkyl, C1-C4 alkoxy, or alogenated C1-C4 alkoxy. In still another embodiment, each R1 is independently chloro, fluoro, C1-C4 alkyl, fluorinated C1-C4 alkyl, C1-C4 alkoxy, or fluorinated C1-C4 alkoxy. In still another embodiment, each R1 is fluoro, C1-C4 alkyl, (CH2)0-3CF3, C1-C4 alkoxy, or O(CH2)0-3CF3. In yet another embodiment, each R1 is independently fluoro, methyl, ethyl, trifluoromethyl, 2,2,2-trifluoroethyl, methoxy, ethoxy, trifluoromethoxy, or 2,2,2-trifluoroethoxy.
In the definition of R1, each Ra and Rb is independently hydrogen, C1-C4 alkyl, or (CH2)0-3CF3. In one embodiment, each Ra and Rb is independently hydrogen, methyl, ethyl, or CF3.
The integer m defines the number of R1 groups which may be present in Compounds I, II-C, and III, and has a value in the range of from 0 to 4. In other embodiments, m is 0 to 3; or is 1 to 3; or is 0 to 2; or is 1 to 2; or is 0 to 1; or is 0.
The group R2 in the definition of Compound II-C and III is C1-C6 alkyl. In one embodiment, R2 is C1-C4 alkyl. In other embodiments, R2 is methyl or ethyl; or is ethyl; or is methyl.
The group X in the definition of Compound II-C is halo. In one embodiment, X is chloro, bromo, or iodo. In other embodiments, X is chloro or bromo; or is bromo; or is chloro.
In Step C acid halide II-C is added to a solution of AlCl3. The solution of AlCl3 can be prepared by dissolving AlCl3 in an organic solvent, typically under an inert atmosphere (e.g., nitrogen or a noble gas such as argon). Suitable organic solvents include halogenated hydrocarbons selected from the group consisting of C1-C6 linear and branched halogenated alkanes, C2-C6 linear and branched halogenated alkenes, C5-C7 halogenated cycloalkanes, and C6-C10 halogenated aromatic hydrocarbons. Exemplary solvents include carbon tetrachloride, chloroform, methylene chloride, 1,2-dichloroethane (DCE), 1,1,2-trichloroethane (TCE), 1,1,2,2-tetrachloroethane, chlorocyclohexane, benzyl chloride, benzyl bromide, chloro- and bromo-benzene, and chloro- and bromo-toluenes. In one embodiment, the solvent is a C1-C4 linear or branched halogenated alkane. In an aspect of the preceding embodiment, the solvent is methylene chloride.
Prior to addition of acid halide II-C, the AlCl3 solution is cooled to a temperature of less than about 0xc2x0 C. The acid halide is added to the AlCl3 solution while maintaining the temperature at or below about 0xc2x0 C. The acid halide can be added as a solid, but is more typically added in solution form using, e.g., the same solvent used in the AlCl3 solution (e.g., methylene chloride). The acid halide II-AlCl3-solvent mixture is maintained at a temperature at or below about 0xc2x0 C. until the desired degree of conversion has been obtained, after which the reaction can be quenched by addition of an aqueous strong acid.
The temperature in Step C is typically in a range of from about xe2x88x9240 to about 0xc2x0 C., and is more typically in a range of from about xe2x88x9220 to about 0xc2x0 C. (e.g., from about xe2x88x9220 to about xe2x88x925xc2x0 C.).
Any amount of AlCl3can be employed in Step C which results in the formation of at least some of Compound III. Of course, the maximum conversion of Compound II-C and maximum yield of Compound III is normally desired, and relative proportions of reactants and reagents suitable for this purpose are typically employed. AlCl3 can be employed in an amount of at least about 0.1 equivalent per equivalent of Compound II-C, and is typically employed in an amount of at least about 0.5 equivalent per equivalent of Compound II-C. In one embodiment, AlCl3 is employed in an amount in the range of from about 0.5 to about 5 equivalents per equivalent of Compound II-C. In another embodiment, the amount of AlCl3 is in the range of from about 2 to about 3 equivalents per equivalent of II-C.
Step D involves the cleavage of the alkylcarbonyloxy group in Compound III with an alkali metal (hydro)peroxide in organic solvent to afford hydroxychromanone I. Suitable organic solvents for Step D include those selected from the group consisting of dialkyl ethers wherein each alkyl is independently a C1-C6 alkyl, C4-C8 dialkoxyalkanes, C4-C6 cyclic ethers and diethers, C6-C8 aromatic ethers, and C1-C6 alkyl alcohols. Exemplary solvents include ethyl ether, MTBE, THF, dioxane, 1,2-dimethoxyethane (DME), anisole, phenetole, methanol, ethanol, n- and iso-propanol, and tert-butyl alcohol. In one embodiment, the solvent is selected from the group consisting of dialkyl ethers wherein each alkyl is independently a C1-C4 alkyl, C4-C6 cyclic ethers and diethers, and C1-C4 alkyl alcohols. In an aspect of the preceding embodiment, the solvent is a dialkyl ether or a cyclic ether. In another aspect of the preceding embodiment, the solvent is THF.
The alkali metal (hydro)peroxide can be the peroxide or hydroperoxide of any of the alkali metals, but is typically lithium peroxide or lithium hydroperoxide. In one embodiment, the alkali metal (hydro)peroxide is LiOOH. The alkali metal (hydro)peroxide can be prepared by reacting an alkali metal basic salt (e.g., a hydroxide such as LiOH) with hydrogen peroxide in a ratio of at least one equivalent of peroxide per equivalent of alkali metal. Alkali metal peroxide (e.g., LiOOH) can be obtained, for example, by admixing the corresponding metal hydroxide (1 equivalent) dispersed or suspended in an ether solvent (e.g., THF) with aqueous H2O2 (1 equivalent).
Any amount of the (hydro)peroxide can be employed in Step D which results in the formation of at least some of Compound I. Of course, the maximum conversion of Compound III and maximum yield of Compound I is normally desired, and relative proportions of (hydro)peroxide and Compound III suitable for this purpose are typically employed. The (hydro)peroxide can be employed in an amount of at least about 0.5 equivalent per equivalent of Compound II, and is typically employed in an amount of at least about 1 equivalent per equivalent of Compound III. In one embodiment, the (hydro)peroxide is employed in an amount in the range of from about 1 to about 5 equivalents per equivalent of Compound III. In another embodiment, the amount of (hydro)peroxide is in the range of from about 1 to about 3 equivalents per equivalent of III.
Step D is suitably conducted at a temperature at or below about xe2x88x920xc2x0 C., and is typically conducted at a temperature in the range of from about 40 to about 0xc2x0 C. In one embodiment, the temperature is in the range of from about xe2x88x9220 to about 0xc2x0 C. (e.g., from about xe2x88x9220 to about xe2x88x925xc2x0 C.).
The reaction of Step D can be conducted by cooling a solution or suspension of the alkali metal (hydro)peroxide in suitable solvent (e.g., an ether such as THF) to the desired temperature at or below about 0xc2x0 C., followed by the slow addition of a solution of Compound III in the same solvent. The mixture can then be maintained at low temperature until the desired degree of conversion is obtained, after which the reaction can be quenched (e.g., by addition of an aqueous solution of sodium bisulfite).
The products of Steps C and D (i.e., Compounds III and I respectively) can be recovered from their respective reaction mixtures at the conclusion of the reaction by conventional means; e.g., isolation from the quenched reaction mixtures using conventional techniques such as solvent extraction, chromatography, or distillation.
Another embodiment of the present invention is a process for preparing hydroxychromanone I via Steps C and D as heretofore described, which further comprises:
(B) treating a compound of Formula (II-B): 
xe2x80x83with an acyl halide reagent to form Compound II-C, wherein xcex1, R1 and R2 are as defined above.
An aspect of the preceding embodiment is a process for preparing hydroxychromanone I* via Steps C and D as heretofore described, which further comprises:
(B) treating a compound of Formula (II-B*): 
xe2x80x83with an acyl halide reagent to form Compound II-C*, wherein xcex1, R1 and R2 are as defined above.
Suitable acyl halide reagents include PCl3, PCl5, PBr3, PBr5, SOCl2, oxalyl chloride, and oxalyl bromide. Step B is typically conducted in an aprotic organic solvent such as a solvent selected from the group consisting of C3-C12 linear and branched alkanes, C1-C6 linear and branched halogenated alkanes, C5-C7 cycloalkanes and halogenated derivatives thereof, C6-C10 aromatic hydrocarbons and halogenated derivatives thereof, dialkyl ethers wherein each alkyl is independently a C1-C6 alkyl, C4-C8 dialkoxyalkanes, C4-C6 cyclic ethers and diethers, C6-C8 aromatic ethers. Examples of such solvents are set forth above in the description of the suitable solvents for Steps C and/or D. In one embodiment, the solvent is a C1-C4 linear or branched halogenated alkane. In an aspect of the preceding embodiment, the solvent is methylene chloride.
Step B is suitably conducted at a temperature in a range of from about 0 to about 60xc2x0 C., and is typically conducted at a temperature of from about 5 to about 40xc2x0 C.
Any amount of acyl halide reagent can be employed in Step B which results in the formation of at least some of Compound II-C. Of course, the maximum conversion of Compound II-B and maximum yield of Compound II-C is normally desired, and relative proportions of reagent and Compound II-B suitable for this purpose are typically employed. The acyl halide reagent can be employed in an amount of at least about 0.5 equivalent per equivalent of Compound II-B, and is typically employed in an amount of at least about 1 equivalent per equivalent of Compound II-B. In one embodiment, the reagent is employed in an amount in the range of from about 1 to about 3 equivalents per equivalent of Compound II-B.
The reaction of Step B can optionally be conducted in the presence of a catalytic amount of an amide including the dialkyl carboxylic acid amides (e.g., dimethylformamide and dimethylacetamide), and NMP. In one embodiment, an amide is present in an amount of at least about 0.01 equivalent per equivalent of Compound II-B. In another embodiment, an amide is present in an amount in a range of from about 0.05 to about 0.5 equivalent per equivalent of Compound II-B.
The reaction of Step B can be conducted by adding the acyl halide reagent (e.g., oxalyl chloride) to a solution of the acid II-B in an aprotic organic solvent, optionally followed by the addition of the amide. The resulting mixture can then be agitated (e.g., stirred) at reaction temperature until the desired degree of conversion is obtained. Product II-C can be recovered from the reaction mixture by conventional means.
Another embodiment of the present invention is a process for preparing hydroxychromanone I via Steps B, C and D as described above, which further comprises:
(A) treating a compound of Formula (II-A): 
xe2x80x83with an acylating agent of Formula (IV): 
in the absence of base, to form Compound II-B;
wherein Y is halo;
and xcex1, m, R1 and R2 are as already defined.
An aspect of the preceding embodiment is a process for preparing hydroxychromanone I* via Steps B, C and D as described above, which further comprises:
(A) treating a compound of Formula (I-A*): 
xe2x80x83with an acylating agent of Formula (IV): 
in the absence of base, to form Compound II-B*;
wherein m, R1, R2 and Y are as already defined.
In one embodiment of Step A, Y is chloro, bromo, or iodo. In other embodiments, Y is chloro or bromo; or is bromo; or is chloro. Exemplary acylating agents include the acetyl chloride, acetyl bromide, propionyl chloride, propionyl bromide, butyryl chloride, isobutyryl chloride, valeryl chloride, and isovaleryl chloride. In one embodiment, the acylating agent is acetyl chloride; i.e., R2 is methyl and Y is chloro.
Step A is typically conducted in a solvent selected from C1-C6 linear and branched halogenated alkanes, C5-C7 cycloalkanes and halogenated derivatives thereof, C6-C10 aromatic hydrocarbons and halogenated derivatives thereof, dialkyl ethers wherein each alkyl is independently a C1-C6 alkyl, C4-C8 dialkoxyalkanes, C4-C6 cyclic ethers and diethers, and C6-C8 aromatic ethers. Examples of such solvents are set forth above in the description of the suitable solvents for Steps C and/or D. In one embodiment, the solvent is a dialkyl ether. In an aspect of the preceding embodiment, the solvent is MTBE.
Step A is suitably conducted at a temperature in a range of from about 40xc2x0 C. to reflux, and is typically conducted at a temperature of from about 50xc2x0 C. to reflux. The reflux temperature of the mixture will of course depend upon the choice and relative amounts of the acylating agent, Compound II-A, and solvent.
Any amount of acylating agent can be employed in Step A which results in the formation of at least some of Compound II-B. Of course, the maximum conversion of Compound II-A and maximum yield of Compound II-B is normally desired, and relative proportions of acylating agent and Compound II-A suitable for this purpose are typically employed. The acylating agent can be employed in an amount of at least about 1 equivalent (e.g., from about 1 to about 20 equivalents) per equivalent of Compound II-A, and is typically employed in an amount of at least about 2 equivalents (e.g., from about 2 to about 10 equivalents) per equivalent of Compound II-A. In one embodiment, the reagent is employed in an amount of at least about 5 equivalents (e.g., from about 5 to about 10 equivalents) per equivalent of Compound II-A.
The reaction of Step A can be conducted by adding acylating agent (e.g., acetyl chloride) to a solution or suspension of the hydroxyacid II-A in solvent, and then heating the mixture to reflux. The mixture can then be maintained at reflux until the desired degree of conversion is obtained, optionally with periodic addition of additional portions of acylating agent. Product II-B can be recovered from the reaction mixture by conventional means (e.g., by cooling the reaction mixture and concentrating via heat or vacuum distillation).
The present invention also includes a process for preparing an oxime of Formula (VI) which comprises Steps C and D (and optionally Step B or both Steps A and B) as described above, and further comprises:
(E) treating Compound I with a hydroxylamine of Formula (V):
H2Nxe2x80x94OR3xe2x80x83xe2x80x83(V),
xe2x80x83or an acid salt thereof, to form an oxime of Formula (VI): 
xe2x80x83wherein R3 is
(1) hydrogen;
(2) C1-C6 alkyl;
(3) C1-C6 alkyl substituted with one or more substituents, each of which is independently halo, cyano, C1-C4 alkoxy, C1-C4 haloalkoxy, C3-C8 cycloalkyl, or phenyl;
(4) C3-CS cycloalkyl;
(5) C3-C8 cycloalkyl substituted with one or more substituents, each of which is independently halo, cyano, C1-C4 alkyl, C1-C4 haloalkyl, C1-C4 alkoxy, C1-C4 haloalkoxy, or phenyl;
(6) phenyl; or
(7) phenyl substituted with one or more substituents, each of which is independently C1-C4 alkyl, C1-C4 haloalkyl, C1-C4 alkoxy, C1-C4 haloalkoxy, cyano, or halo; and
xe2x80x83xcex1, R1 and m are as already defined above.
An aspect of the preceding embodiment is a process for preparing an oxime of Formula (VI*) which comprises Steps C and D (and optionally Step B or both Steps A and B) as described above, and further comprises:
(E) treating Compound I with a hydroxylamine of Formula (V):
H2Nxe2x80x94OR3xe2x80x83xe2x80x83(V),
xe2x80x83or an acid salt thereof, to form an oxime of Formula (VI*): 
xe2x80x83wherein xcex1, R1, R3 and m are as already defined above.
In an embodiment of Step E, R3 in the definition of Compounds V and VI is (1) hydrogen; (2) C1-C4 alkyl; or (3) C1-C4 alkyl substituted with one or more substituents, each of which is independently halo, cyano, C1-C4 alkoxy, C1-C4 haloalkoxy, C3-C8 cycloalkyl or phenyl. In other embodiments, R3 is hydrogen, methyl, ethyl, phenyl, or benzyl; or is hydrogen.
Hydroxylamine V can be employed in Step E as a free base or more typically as an acid salt. Suitable salts include salts of mineral acids such as sulfate salts and hydrohalide salts. In one embodiment, Compound V is the sulfate salt (e.g., hydroxylamine sulfate). In another embodiment, Compound V is hydroxylamine, methoxylarmine, or benzyloxylamine, or a sulfate or hydrochloride salt thereof. In an aspect of the preceding embodiment, Compound V is the sulfate salt of hydroxylamine.
The reaction is typically conducted in a polar organic solvent such as an ether or an alcohol optionally in admixture with water as a co-solvent. Suitable ethers and alcohols include the dialkyl and aromatic ethers, dialkoxyalkanes, cyclic ethers and diethers, and aliphatic alcohols described and defined above for other process steps. The water can comprise from about 5 to about 95 volume percent based on the total volume of solvent, but the amount of water is typically in the range of from about 10 to about 50 volume percent. When an aqueous system is employed, a buffering salt such as sodium acetate is typically employed as well.
Step E is suitably conducted at a temperature in a range of from about 5xc2x0 C. to about 40xc2x0 C., and is typically conducted at a temperature of from about 10 to bout 40xc2x0 C. In one embodiment, the reaction temperature is in a range of from about 15 to about 30xc2x0 C. (e.g., from about 15 to about 25xc2x0 C.).
Any amount of hydroxylamine V can be employed in Step E which results in the formation of at least some of oxime VI. Of course, the maximum conversion of hydroxychromanone I and maximum yield of oxime VI is normally desired, and relative proportions of Compounds I and V for this purpose are typically employed. The hydroxylamine V can be employed in an amount of at least about 1 equivalent (e.g., from about 1 to about 10 equivalents) per equivalent of Compound I, and is typically employed in an amount of at least about 2 equivalents (e.g., from about 2 to about 5 equivalents) per equivalent of Compound I.
The reaction of Step E can be conducted by adding hydroxylamine V, water, and optionally buffer (e.g., NaOAc) to a solution or suspension of the hydroxychromanone I in a polar solvent (e.g., THF), and then agitating (e.g., stirring) the two-phase mixture at a controlled temperature (e.g., room temperature=about 25xc2x0 C.) until the desired degree of conversion is obtained. The oxime product can be recovered by separating the layers, washing and drying the organic layer, and then filtering and concentrating the organic layer. The oxime product is typically a mixture of the E and Z geometrical isomers, both of which consisting substantially of the 3(R) hydroxy optical isomer.
The present invention also includes a process for preparing an aminochromanol of Formula (VII) which comprises Steps C, D and E (and optionally Step B or both Steps A and B) as described above, and further comprises:
(F) hydrogenating in the presence of a palladium catalyst a mixture comprising Compound VI, a third organic solvent, and HBr to form an aminochromanol of Formula (VII): 
xe2x80x83wherein stereocenters xcex1 and xcex2 are either both in the R configuration or both in the S configuration, and R1 and m are as already defined above.
An embodiment of this process is a process for preparing an aminochromanol of Formula (VII*) which comprises Steps C, D and E (and optionally Step B or both Steps A and B) as described above, and further comprises:
(F) hydrogenating in the presence of a palladium catalyst a mixture comprising Compound VI*, a third organic solvent, and HBr to form an aminochromanol of Formula (VII*): 
xe2x80x83wherein R1 and m are as already defined above.
Suitable solvents for Step F can be selected from the group consisting of C3-C12 linear and branched alkanes, C1-C6 linear and branched halogenated alkanes, C5-C7 cycloalkanes, C6-C10 aromatic hydrocarbons, dialkyl ethers wherein each alkyl is independently a C1-C6 alkyl, C4-C8 dialkoxyalkanes, C4-C6 cyclic ethers and diethers, C6-C8 aromatic ethers, and C1-C6 alkyl alcohols. Exemplary solvents include carbon tetrachloride, chloroform, methylene chloride, 1,2-dichloroethane (DCE), 1,1,2-trichloroethane (TCE), 1,1,2,2-tetrachloroethane, cyclohexane, toluene, o- and m- and p-xylene, ethylbenzene, ethyl ether, MTBE, THF, dioxane, 1,2-dimethoxyethane (DME), anisole, phenetole, methanol, ethanol, n- and iso-propanol, and tert-butyl alcohol.
In one embodiment, the solvent is selected from the group consisting of C2-C6 linear and branched halogenated alkanes, dialkyl ethers wherein each alkyl is independently a C1-C4 alkyl, C4-C6 cyclic ethers and diethers, and C1-C4 alkyl alcohols. In an aspect of the preceding embodiment, the solvent is a C1-C4 alkyl alcohol. In another aspect of the preceding embodiment, the solvent is methanol.
The solvent can also be a mixture comprising water and an organic co-solvent. Suitable co-solvents include the organic solvents set forth in the preceding two paragraphs. In one embodiment, the co-solvent is a C1-C6 monohydric alcohol. In an aspect of this embodiment, the co-solvent is methanol or ethanol. The water can comprise from about 5 to about 95 volume percent based on the total volume of solvent. It has been found, however, that significant amounts of water (i.e., more than about 20 volume percent) can reduce the cis/trans selectivity of the hydrogenation. The use of 1:2 methanol/water solvent systems with HBr, for example, has been found to reduce selectivity dramatically compared to the use of methanol alone (e.g., 11:1 v. 23:1). Accordingly, in a preferred embodiment, the amount of water in the water-organic co-solvent mixture (e.g., water/methanol) is no more than about 20 vol%.
The hydrogenation of the oxime VI can be conducted over a wide range of temperatures, although the temperature is typically in the range of from about xe2x88x9225 to about 200xc2x0 C. (e.g., from about xe2x88x9220 to about 100xc2x0). In one embodiment, the temperature is in the range of from about xe2x88x9210 to about 20xc2x0 C. In another embodiment, the temperature is from about xe2x88x925 to about 5xc2x0 C.
The pressure is not a critical aspect in Step F, although atmospheric and superatmospheric pressures tend to be expedient. In one embodiment, the pressure is at least about 2 psig (115 kPa). In another embodiment, the pressure is in the range of from about 10 psia (68.9 kPa) to about 10,000 psia (68,950 kPa) (e.g., from about 50 psia (345 kPa) to about 1,000 psia (6,895 kPa)).
In one embodiment, the hydrogenation is conducted at a temperature in the range of from about xe2x88x9220 to about 100xc2x0 C. and at a pressure of from about 2 psig (115 kPa) to about 1000 psig (6996 kPa). In another embodiment, the hydrogenation is conducted at a temperature in the range of from about xe2x88x925 to about 20xc2x0 C. and at a pressure in the range of from about 10 psig (167 kPa) to about 500 psig (3549 kPa). In still another embodiment, the hydrogenation is conducted at a temperature in the range of from about xe2x88x9210 to about 10xc2x0 C. and at a pressure in the range of from about 10 psig (170 kPa) to about 100 psig (791 kPa).
The hydrogenation catalyst comprises palladium, which can be supported or unsupported. Suitable catalyst supports include carbon, silica, alumina, silicon carbide, aluminum fluoride, and calcium fluoride. Exemplary palladium catalysts include Pd black (i.e., fine metallic palladium particles) and Pd/C (i.e., palladium on a carbon support). Pd black is an effective catalyst, but results have been found to depend upon on the choice of vendor. Pd/C is a preferred catalyst.
The hydrogen source is typically hydrogen gas, optionally in admixture with a carrier gas that is inert to the process of the invention (e.g., nitrogen or a noble gas such as helium or argon).
The hydrogenation can be carried out in batches or continuously in various types of reactors such as a fixed bed reactor or an agitated slurry reactor in which the slurry of gas, solvent, oxime VI, HBr, and Pd catalyst is continuously agitated by mechanical or gas means. A suitable reaction vessel for relatively small scale, batch-wise hydrogenations is an autoclave equipped with a stirrer or rocker to agitate the reaction mixture. In a batch process, the order of addition of oxime VI, solvent, acid, and hydrogenation catalyst to the reaction vessel (also referred to herein as the reaction xe2x80x9cpotxe2x80x9d) is not critical. The reactants and reagents can, for example, be added concurrently, either together or separately, or they can be added sequentially in any order. In one embodiment, oxime VI pre-mixed with the solvent is charged to the reaction vessel followed by addition of HBr, and then the Pd catalyst. The hydrogenation can then be conducted by charging hydrogen gas, optionally in admixture with one or more inert gases, to the vessel containing the mixture comprising oxime VI, solvent, HBr and Pd catalyst, and then agitating the mixture under reaction conditions.
Any amount of HBr, Pd catalyst and hydrogen can be employed which results in the formation of at least some of Compound VII. Of course, the maximum conversion of Compound VI and maximum yield of Compound VII is normally desired, and relative proportions of reactants and reagents suitable for this purpose are typically employed.
The HBr is suitably employed in Step F in an amount of at least about 0.5 equivalents per equivalent of Compound VI, and is typically employed in an amount of at least about 1 equivalent per equivalent of Compound VI. In one embodiment, the HBr is employed in an amount in the range of from about 0.5 to about 2 equivalents per equivalent of Compound VI. In another embodiment, the amount of HBr is in the range of from about 0.75 to about 1.25 equivalents per equivalent of VI. In still another embodiment, the amount of HBr is in the range of from about 0.95 to about 1.05 equivalents per equivalent of VI.
In one aspect of the process, the amount of HBr is in the range of from about 0.95 to about 1.05 equivalents per equivalent of VI, and the hydrogenation temperature is in the range of from about xe2x88x925 to about 5xc2x0 C. In another aspect of the process, the catalyst is Pd/C, the amount of HBr is in the range of from about 0.95 to about 1.05 equivalents per equivalent of VI, and the hydrogenation temperature is in the range of from about xe2x88x925 to about 5xc2x0 C.
When the level of HBr employed in the process is greater about 1.25 equivalents, hydrogenation should be begun promptly after the addition of the acid to avoid formation of solvolysis by-products such as, when using methanol solvent, 
The uptake of hydrogen is not a critical process parameter, although at least a stoichiometric amount of hydrogen gas is typically employed.
Any amount of Pd catalyst can be employed which results in the formation of at least some of Compound VII. The amount of catalyst employed in step F is suitably at least about 0.01 mole percent Pd, and is typically in the range of from about 0.01 to about 5 (e.g., from about 0.1 to about 5) mole percent Pd, based on the total moles of Pd metal and Compound VII. In one embodiment, the amount of catalyst is in the range of from about 1 to about 5 (e.g., from about 2 to about 3) mole percent Pd metal.
The progress of any of the above-described reaction steps (i.e., Steps A, B, C, D, E and F) can be followed by monitoring the disappearance of a reactant (e.g., Compound VI or H2 in Step F) and/or the appearance of the product using such analytical techniques as TLC, HPLC, NMR or GC.
The product resulting from the hydrogenation of oxime VI is typically in the form of an HBr salt, which can be treated with a base to provide free amine. Any organic or inorganic base which is capable of neutralizing the acidic hydrogenated mixture resulting from step F can be employed. Suitable bases include bases selected from the group consisting of alkali metal hydroxides, alkali metal carbonates, alkali metal oxides, C1-C6 alkoxides of alkali metals, alkaline earth metal hydroxides, alkaline earth metal oxides, tetra (C1-C4 alkyl)ammonium hydroxides, and tri-(C1-C4 alkyl)amines. Exemplary bases include hydroxides, carbonates, and oxides of lithium, sodium and potassium; methoxides, ethoxides, and n- and iso-propoxides of lithium, sodium, and potassium; tetramethyl- and tetraethyl-ammonium hydroxide; triethylamine; and diisopropylethylamine. In one embodiment, the base is selected from the group consisting of alkali metal hydroxides. In an aspect of the preceding embodiment, the base is NaOH or KOH.
The base is typically employed in an amount sufficient to achieve complete neutralization of the Step F reaction product. The amount of base can suitably be at least about 1 equivalent per equivalent of Compound VII, and is typically in the range of from about 1 to about 5 equivalents per equivalent of Compound VII. In one embodiment, the amount of base is from about 1 to about 2 equivalents per equivalent of Compound VII. In another embodiment, the amount of base is in the range of from about 1 to about 1.5 equivalents per equivalent of Compound VII. The base can be charged to the reaction vessel containing the step F hydrogenated mixture, or the hydrogenated mixture can be charged to a vessel containing the base.
The base neutralization can be suitably conducted at a temperature in the range of from about xe2x88x9210 to about 110xc2x0 C., and is typically conducted at a temperature in the range of from about 0 to about 80xc2x0 C. In one embodiment, the temperature is in the range of from about 10 to about 30xc2x0 C.
Alternatively, the base treatment of the Step F product can comprise eluting the hydrogenated mixture through a suitable ion exchange column, such as elution through Dowex(copyright) (available from Dow Chemical) or Amberlyst-IRA (available from Rohm and Haas).
Following the treatment with base, Compound VII in a free base form can be isolated from the reaction mixture by conventional means, such as by filtration to remove solids, solvent wash, concentration (e.g., by vacuum removal of solvent), and crystallization.
It is to be understood that, unless stated to the contrary, any references herein to Compounds I, II-A, II-B, II-C, III, VI, and VII also apply to Compounds I*, II-A*, II-B*, II-C*, III*, VI* and VII*.
The crude cis-aminochromanol product VII obtained from Step F is enantiomerically enriched in either the S,S-isomer or the R,R-isomer; i.e., the product has an significant enantiomeric excess (ee) of the S,S-isomer over the R,R-isomer or vice versa. Product VII may suitably be characterized as having an ee of at least about 60%, and typically has an ee of at least about 90%. The product can have an ee of 95% or more (e.g., 99%). To the extent that product VII is a mixture of optical isomers, the desired isomer (either S,S- or R,R) can be purified by forming diastereomeric salts of the isomers and separating the salts by fractional crystallization. In one embodiment, the isomer of Compound VII can be purified by:
(1) forming a solution comprising Compound VII, a chiral acid, and solvent;
(2) crystallizing from the solution a salt which contains predominantly either the S,S- or R,R-isomer; and
(3) if the precipitated salt crystals consist predominantly of the desired isomer, separating the salt crystals from the mother liquor; and
(4) if the mother liquor consists predominantly of the desired isomer, separating the salt crystals from the mother liquor and recovering the isomer from the mother liquor.
In an aspect of the preceding embodiment, the S,S-isomer (i.e., Compound VII*) can be purified by:
(1) forming a solution comprising Compound VII*, a chiral acid, and solvent;
(2) crystallizing from the solution a salt which contains predominantly either the S,S- or R,R-isomer; and
(3) if the precipitated salt crystals consist predominantly of the S,S-isomer, separating the salt crystals from the mother liquor; and
(4) if the mother liquor consists predominantly of the S,S-isomer, separating the salt crystals from the mother liquor and recovering the S,S-isomer from the mother liquor.
Suitable chiral acids include optically active forms of tartaric acid, mandelic acid, camphoric acid, 10-camphorsulfonic acid, pyroglutamic acid, O,O-diacetyltartaric acid, O,O-dibenzoyltartaric acid, O,O-di-4-toluyltartaric acid, and N-acetyl derivatives of amino acids such as N-acetylleucine. A preferred chiral acid is (S)-mandelic acid or (R)-mandelic acid. The chiral acid is especially (S)-mandelic acid, and the crystallized (S)-mandelate salt resulting from crystallizing step (2) is a salt of the S,S-isomer.
The solvent can be any organic or inorganic substance, or combinations thereof, which can dissolve Compound VII and the chiral acid and is chemically inert thereto. Suitable solvents include water, C1-C6 monohydric alcohols (e.g., methanol, ethanol, n-propanol, n-butanol, n-pentanol, isopropanol, and sec-butyl alcohol), C2-C8 polyhydric alcohols (e.g., ethylene glycol, propylene glycol, and glycerol), C1-C4 nitrites (e.g., acetonitrile and propionitrile), N,N-di-C1-C6 alkyl tertiary amides of C1-C6 alkylcarboxylic acids (e.g., DMF), aliphatic C2-C6 ethers and di-ethers (e.g., ethyl ether, MTBE and dimethoxyethane), and C4-C6 cyclic ethers and di-ethers (e.g., THF and dioxane). In one embodiment, the solvent is selected from the group consisting of C1-C6 monohydric alcohols, aliphatic C2-C6 ethers and di-ethers and C4-C6 cyclic ethers and di-ethers. In an aspect of the preceding embodiment, the solvent is an alcohol such as methanol or ethanol.
In another embodiment, the solvent is a mixture comprising water and an organic co-solvent. In an aspect of this embodiment, water comprises at least about 5 volume percent of the solvent (e.g., from about 5 to about 95 volume percent) based on the total volume of solvent. In another aspect of this embodiment, the aqueous solvent comprises from about 30 to about 70 volume percent (e.g., from about 40 to about 60 volume percent) water, with the balance of the solvent being organic co-solvent. Suitable co-solvents include the organic solvents set forth in the preceding paragraph. In one embodiment, the co-solvent is a C1-C6 monohydric alcohol. In an aspect of this embodiment, the co-solvent is methanol or ethanol.
The crystallization of the S,S- or R,R-isomer as set forth in step (2) above can be accomplished using conventional techniques, such as by cooling the solution or by concentrating the solution via vacuum or evaporative removal of solvent. If the resulting crystals are predominantly the S,S-isomer, the crystals can then be separated by filtration and followed optionally by the washing and drying of the filter cake. If the precipiated crystals are predominantly the R,R-isomer, a salt which contains predominantly the S,S isomer can be obtained from the mother liquor, such as by evaporative or vacuum removal of the solvent.
The crystallized salt of the recovered isomer (e.g., the S,S-isomer) can then be broken by treating the salt with base. In a typical procedure, the crystallized salt can be slurried in an organic solvent, the slurry mixed with aqueous base resulting in a biphasic mixture, and the organic layer containing the isomer separated from the aqueous layer. The formation of the slurry and the biphasic mixture is suitably conducted at temperatures in the range of from about 0 to about 100xc2x0 C., and is typically conducted at a temperature of from about 10 to about 60xc2x0 C. In one embodiment, the temperature is in the range of from about 15 to about 35xc2x0 C. The base can be any of the bases set forth above in the description of treating the HBr salt of aminochromanol VII. The base can also be an alkanolamine (e.g., ethanolamine), a hydroxylamine (e.g., hydroxylamine per se, N-methylhydroxylamine, N,N-dimethylhydroxylamine, or N-ethylhydroxylamine), or a diamine (e.g., ethylenediamine, tetramethylenediamine, or hexamethylenediamine). The organic solvent can suitably be selected from C1-C12 linear and branched alkanes, C1-C12 linear and branched halogenated alkanes, C5-C10 cycloalkanes, C6-C14 aromatic hydrocarbons, dialkyl ethers wherein each alkyl is independently a C1-C10 alkyl, C4-C8 dialkoxyalkanes, C4-C8 cyclic ethers and diethers, C6-C8 aromatic ethers, C2-C10 dialkyl ketones wherein each alkyl is independently C1-C8 alkyl, C1-C6 alkyl esters of C1-C6 alkylcarboxylic acids, primary C1-C10 alkyl alcohols, secondary C3-C10 alkyl alcohols, tertiary C4-C10 alkyl alcohols, primary amides of C1-C6 alkylcarboxylic acids, Nxe2x80x94C1-C6 alkyl secondary amides or N,N-di-C1-C6 alkyl tertiary amides of C1-C6 alkylcarboxylic acids, C2-C6 aliphatic nitriles, and C7-C10 aromatic nitriles. Exemplary solvents include carbon tetrachloride, chloroform, methylene chloride, 1,2-dichloroethane (DCE), 1,1,2-trichloroethane (TCE), 1,1,2,2-tetrachloroethane, cyclohexane, toluene, o- and m- and p-xylene, ethylbenzene, ethyl ether, MTBE, THF, dioxane, 1,2-dimethoxyethane (DME), anisole, phenetole, acetone, methyl ethyl ketone (MEK), methyl acetate, ethyl acetate, IPAc, ethanol, n- and iso-propanol, tert-butyl alcohol, dimethylformamide (DMF), acetonitrile, propionitrile, benzonitrile, and p-tolunitrile.
In an aspect of the process of purifying the S,S-optical isomer VII*, a solution of cis-aminochromanol and (S)-mandelic acid is formed, the (S)-mandelate salt of the S,S-isomer is crystallized and separated from the mother liquor, and the crystallized salt is broken by treatment with ethanolamine to afford the purified S,S-aminochromanol isomer.
Another embodiment of the process of the invention is a process for preparing hydroxychromanone 6: 
which comprises:
(C) adding acid chloride 4a: 
xe2x80x83to a solution of AlCl3 in a halogenated hydrocarbon solvent at a temperature of less than about 0xc2x0 C. to form acetoxy chromanone 5: 
(D) reacting Compound 5 at a temperature of less than about 0xc2x0 C. with lithium peroxide or lithium hydroperoxide in an ethereal or alcoholic solvent to form Compound 6.
Aspects of the preceding embodiment include the process as just set forth, wherein:
(i) the temperature in Step C is in a range of from about xe2x88x9220 to about 0xc2x0 C.;
(ii) the halogenated hydrocarbon solvent in Step C is a C1-C6 linear or branched halogenated alkane (e.g., methylene chloride);
(iii) AlCl3is employed in Step C in an amount of from about 0.1 to about 5 equivalents per equivalent of Compound 4a;
(iv) the temperature in Step D is in a range of from about xe2x88x9220 to about 0xc2x0 C.;
(v) the solvent in Step D is selected from the group consisting of dialkyl ethers wherein each alkyl is independently a C1-C4 alkyl, C4-C6 cyclic ethers and diethers, and C1-C4 alkyl alcohols;
(vi) the lithium peroxide or hydroperoxide (e.g., LiOOH) is employed in Step D in an amount of from about 1 to about 5 equivalents per equivalent of Compound 5; and
(vii) the process incorporates one or more of any of aspects (i) to (vi).
In another embodiment of the process of the invention is a process for preparing oxime 7 which comprises Steps C and D as just set forth above and further comprises:
(E) treating Compound 6 with hydroxylamine or an acid salt thereof to form oxime 7: 
Aspects of the preceding embodiment include the process as set forth, wherein:
(i) Compound 6 is treated with hydroxylamine sulfate;
(ii) the temperature is in a range of from about 15 to about 30xc2x0 C.;
(iii) hydroxylamine is employed in an amount of at least about 2 equivalents per equivalent of 6;
(iv) the treating is conducted in a two-phase solvent consisting of an aqueous ether, optionally in the presence of a buffer (e.g., NaOAc); and
(v) the process incorporates one or more of any of aspects (i) to (iv).
In still another embodiment of the process of the invention is a process for preparing aminochromanol 8 which comprises Steps C, D, and E as just set forth above and further comprises:
(F) hydrogenating in the presence of a palladium catalyst a mixture comprising Compound 7, an ethereal or alcoholic solvent, and HBr to form aminochromanol 8: 
Aspects of the preceding embodiment include the process as set forth, wherein:
(i) the catalyst in Step F is Pd/C;
(ii) the amount of HBr is in the range of from about 0.95 to about 1.05 equivalents per equivalent of 7;
(iii) the hydrogenation is conducted at a temperature in the range of from about xe2x88x925 to about 5xc2x0 C.;
(iv) the hydrogenation is conducted at a temperature in the range of from about xe2x88x9220 to about 100xc2x0 C. and at a pressure of at least about 2 psig (115 kPa);
(v) the process incorporates the combination of (i) and (ii);
(vi) the process incorporates the combination of (i) and (iii);
(vii) the process includes the combination of (i), (ii), and (iii); and
(viii) the process includes the combination of (i), (ii) and (iv).
As used herein, the term xe2x80x9cC1-C6 alkylxe2x80x9d (which may alternatively be referred to herein as xe2x80x9cC1-6 alkylxe2x80x9d) means linear or branched chain alkyl groups having from 1 to 6 carbon atoms and includes all of the hexyl alkyl and pentyl alkyl isomers as well as n-, iso-, sec- and t-butyl, n- and isopropyl, ethyl and methyl. xe2x80x9cC1-C4 alkylxe2x80x9d means n-, iso-, sec- and t-butyl, n- and isopropyl, ethyl and methyl. Similar terms (e.g., xe2x80x9cC1-C3 alkylxe2x80x9d) have analogous definitions.
The term xe2x80x9cC1-C6 alkoxyxe2x80x9d means an xe2x80x94O-alkyl group wherein alkyl is C1 to C6 alkyl as defined above. xe2x80x9cC1-C4 alkoxyxe2x80x9d has an analogous meaning; i.e., it is an alkoxy group selected from methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, tert-butoxy, and sec-butoxy. Similar terms (e.g., xe2x80x9cC1-C3 alkoxyxe2x80x9d) have analogous definitions.
The term xe2x80x9chalogenxe2x80x9d (which may alternatively be referred to as xe2x80x9chaloxe2x80x9d) refers to fluorine, chlorine, bromine and iodine (alternatively, fluoro, chloro, bromo, and iodo).
The term xe2x80x9chalogenated C1-C6 alkylxe2x80x9d (which may alternatively be referred to as xe2x80x9cC1-C6 haloalkylxe2x80x9d or xe2x80x9cC1-6 haloalkylxe2x80x9d) means a C1 to C6 linear or branched alkyl group as defined above with one or more halogen substituents. The terms xe2x80x9chalogenated C1-C4 alkylxe2x80x9d and xe2x80x9chalogenated C1-C3 alkylxe2x80x9d have analogous meanings. The term xe2x80x9cfluorinated C1-C6 alkylxe2x80x9d (or xe2x80x9cC1-C6 fluoroalkylxe2x80x9d or xe2x80x9cC1-6 fluoroalkylxe2x80x9d) means a C1 to C6 linear or branched alkyl group as defined above with one or more fluorine substituents. The terms xe2x80x9cfluorinated C1-C4 alkylxe2x80x9d and xe2x80x9cfluorinated C1-C3 alkylxe2x80x9d have analogous meanings. Representative examples of suitable fluoroalkyls include the series (CH2)0-3CF3 and (CH2)0-2CF3 (i.e., trifluoromethyl, 2,2,2-trifluoroethyl, and 3,3,3-trifluoro-n-propyl), 1-fluoroethyl, 2-fluoroethyl, 2,2-difluoroethyl, 3,3,3-trifluoroisopropyl, 1,1,1,3,3,3-hexafluoroisopropyl, and perfluorohexyl.
The term xe2x80x9chalogenated C1-C6 alkoxyxe2x80x9d (which may alternatively be referred to as xe2x80x9cC1-C6 haloalkoxyxe2x80x9d or xe2x80x9cC1-6 haloalkoxyxe2x80x9d) means a C1 to C6 linear or branched alkyl group as defined above with one or more halogen substituents. The terms xe2x80x9chalogenated C1-C4 alkoxyxe2x80x9d and xe2x80x9chalogenated C1-C3 alkoxyxe2x80x9d have analogous meanings. The term xe2x80x9cfluorinated C1-C6 alkoxyxe2x80x9d (which may alternatively be referred to as xe2x80x9cC1-C6 fluoroalkoxyxe2x80x9d) means a C1-C6 alkoxy group as defined above wherein the alkyl moiety has one or more fluorine substituents. The terms xe2x80x9cfluorinated C1-C4 alkoxyxe2x80x9d and xe2x80x9cfluorinated C1-C3 alkoxyxe2x80x9d have analogous meanings. Representative examples include the series O(CH2)0-3CF3 (i.e., trifluoromethoxy, 2,2,2-trifluoroethoxy, 3,3,3-trifluoro-n-propoxy, etc.), 1,1,1,3,3,3-hexafluoroisopropoxy, and so forth.
The term xe2x80x9cC3-C8 cycloalkylxe2x80x9d refers to a cyclic ring selected from cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl. xe2x80x9cC3-C6 cycloalkylxe2x80x9d has an analogous meaning.
The term xe2x80x9calkali metalxe2x80x9d refers to a metal of Group Ia of the Periodic Table, including but not limited to lithium, sodium, and potassium.
Abbreviations used in the instant specification include the following:
Ac=acetic or acetate
AcCl=acetyl chloride
AIDS=acquired immune deficiency syndrome
ARC=AIDS related complex
DCE=1,2-dichloroethane
DME=1,2-dimethoxyethane
DMF=dimethylformamide
DSC=differential scanning calorimetry
EtOH=ethanol
IPAc=isopropyl acetate
KF=Karl Fisher titration for water
Me=methyl
MeCN=acetonitrile
MeOH=methanol
MTBE=methyl tert-butyl ether
NMP=N-methylpyrrolidone
psia=pounds per square inch (absolute)
psig=pounds per square inch (gauge)
THF=tetrahydrofuran
TCE=1,1,2-trichloroethane
XRPD=X-ray powder diffraction
The following examples serve only to illustrate the invention and its practice. The examples are not to be construed as limitations on the scope or spirit of the invention.